The invention is directed to an ignition and fuel injection back-up system for emergency running or starting internal combustion engines in which a Hall sensor drum is driven synchronously with a cam shaft of the engine and delivers a timing pulse to a computer at the beginning of an ignition cycle, the computer controls the ignition, possibly while taking into account additional engine data, and the Hall sensor drum has a cut out portion for every cylinder or every second cylinder, which cut out portions cause a corresponding quantity of timing pulses whose trailing edges occur at a uniform rotational angle before the top dead center of the respective cylinder.
In ignition systems with cylinder recognition, it is known to utilize Hall sensor drums in the ignition distributor, which sensor drum comprises a cut out portion which produces one timing pulse per 720.degree. crankshaft revolution. During the timing pulse, a reference mark is derived e.g. from the toothed rim or from the flywheel of the crankshaft. This reference mark occurs once per revolution of the crankshaft, so that only every second reference mark occurs in the time period of a timing signal. Accordingly, the timing signal and the reference mark together designate the beginning of an ignition cycle from which an exact determination of the optimal ignition times for respective cylinders of the engine can be effected in a microprocesor while taking into account additional engine data, particularly while taking into account the speed or rate of rotation. In the event of the failure of the transmitter for the reference mark or the speed, respectively, in such a system, the engine can no longer continue to be operated.